1. Field of the Invention
The present invention relates to a machine for forming parallel corrugations in a metal sheet, and for welding each of these corrugations at its longitudinal ends.
Metal sheets having parallel corrugations whose lips are welded at their ends are more especially used for forming walls of immersed electric transformers. In fact, these transformers include a tank containing the electric elements which is filled with a liquid dielectric which has the double function of isolating the coils through which the current flows and conveying away the heat dissipated by the transformer in operation. For removing this heat, the tank is provided with radiators of different designs. For the smallest powers, these radiators are formed by more or less deep and closely spaced undulations called corrugations and forming an integral part of the vertical walls of the tank. This technique is at present the most economical and it is more and more widely used.
To manufacture these corrugations in a panel, semi automatic manufacturing lines are used at the present time, the corrugated panels being fabricated in several successive operations so as to obtain a welded and so sealed assembly.
These manufacturing chains are very heavy and expensive and reserved for very large manufacturers.
2. Description of the prior art
A machine of the above mentioned type is already known, as described in the patent FR-A-2 245 427, comprising a bending die whose imprint has, in cross section, the desired shape for each of the corrugations to be formed in a metal sheet. This metal sheet is caused to pass in front of the die and on the side opposite this latter is located a punch or knife whose cross section is a little smaller than that of the die. Means are provided for moving the punch and/or the die perpendicularly to the metal sheet so that, following the movement engaging the punch in the die, the metal sheet is bent inside the die so as to form a corrugation.